The invention discloses a novel method for detaching an existing bridge and culvert structure. The novel method comprises the following steps: reinforcing an existing line by adopting D20 type-A construction temporary beams; filling an existing framework culvert by adopting mortar rubbles; chiselling away a top plate and part side walls of the existing framework culvert downwards from the upper part of the line by utilizing the construction skylight time of the existing line; finally, reinforcing longitudinal and transverse lifting beams of the existing line, and performing jacking construction. According to the novel method, through the construction method, the technical problems that the conventional longitudinal and transverse lifting beam reinforcing method cannot reinforce directly, the construction period is long, the cost is increased and the operation of the existing line is influenced because the distance between the top of the framework culvert and the bottom of a rail is short in the prior art are solved. The invention provides the construction method, which can perform the operations of reinforcing the line and detaching the existing bridge and culvert when the distance between the top of the framework culvert and the bottom of the rail is short, ensure the construction speed, reduce the construction cost, and not affect the operation of the existing line.